Harvesters (e.g. combines) are used to harvest crops. Operations performed by these combines include threshing and separating grain from materials other than grain (MOG). These operations are conventionally performed by a rotor that rotates in a stationary rotor cage. Ideally, as the rotor rotates, the grain is separated from the MOG and falls through perforations in the rotor cage to a grain collection system. The remaining MOG is too big to fall through the perforations and is transported by the rotor towards a residue handling system. This configuration, however, suffers from grain loss, because the rotor and cage are inefficient in separating the grain from the MOG.